Furling of working sails has historically been accomplished by direct manual manipulation of the sail, requiring that one or more of the crew go forward (in the case of a headsail) or at least out of the cockpit (in the case of a mainsail). Furling of working sails is required under various conditions, including conditions of increasing wind and heavier seas. Furling by direct manual manipulation is at best laborious and often unduly dangerous, especially when furling is required during the changing of sails at sea under heavy weather conditions. Accordingly, prior-art workers have long sought to devise both improved methods and improved sail systems in an effort to overcome the disadvantages of manual furling and changing sails.
Prior-art efforts have concentrated mainly on furling of headsails and the most successful of the prior-art systems have been those based on the so-called "roller furling" approach, wherein the luff of the sail is rolled or wound upon either the headstay or a member independent of but adjacent to the headstay. Typical systems of that type are disclosed in U.S. Pat. Nos. 3,611,969 Hood; 3,851,609 Stearn; 3,964,419 Uecker; 3,980,036 Crall; 4,034,694 Dismukes.
Though roller furling systems have achieved rather wide acceptance, they present certain inherent difficulties. Thus, when the roller furling member is of the type which itself must be under tension, the furling member must be supported by bearings and applies a high tension load to the bearings so that the bearings must be serviced frequently and are subject to undue wear. If the furling member encloses and rotates about the headstay, so that the furling member itself is not under tension, torsion problems are encountered since, e.g., a turning moment imparted to the foot of the member is not immediately transmitted to the head of the member, the result being that the furling member is twisted and the sail is not rolled uniformly from head to foot. When the roller furling member is the headstay or directly associated with the headstay, the sail cannot be lowered at all in its furled condition. If the roller furling member is separate from the headstay, the sail can be lowered in its furled condition, but the stiffness and length of the furling member make handling and stowing the furled sail very difficult. Because of the need for a furling drum at the foot, and a swivel at the head, roller furling significantly reduces the length of the headstay which can be occupied by the sail, and eliminates the sail skirt. If roller furling is to be used, the sail must be flat, or virtually flat; the sail can have little or no draft. When the furling member is separate from the headstay, as when a wire member is incorporated in the luff of the sail, the sail exhibits excessive luff sag in all but the lightest of air. Since a roller furled sail is at best difficult to lower in furled condition, the sails are usually left aloft when furled and are thus exposed to the elements for protracted periods. To protect the sail, weather-resistant cover material has been added along the leech and foot, so as to be wound on the outside of the furled sail, but addition of this material, which is relatively heavy, tends, e.g., to collapse the sail in light air. Finally, while roller furling has been applied to mainsails, its use for mainsails is essentially impractical, requiring extensive mast modification and undue limitation of sail area. Such difficulties have generated a continuing need for improvement in the art of furling working sails while aloft.